Long before the al-Qaeda attacks on Washington and New York, American writer Don DeLillo attempted to show in his novel Mao II, named after an Andy Warhol silkscreen, how terrorists and bomb-makers had replaced writers and artists as the leading myth-makers of our age. Mao II was published in 1991, when many in the West thought we were entering a long period of rest following the end of the Cold War. It was received largely with bewilderment and even indifference. What was up with old Don DeLillo? Why this persistent interest in terrorism?

DeLillo was, ahead of the game. He had long understood that, as he wrote in Mao II: 'Terror makes the new future possible.' The major work of terrorists 'involves midair explosions and crumbled buildings. This is the new tragic narrative'.

The arrest last week of 24 people in night-time raids in London, High Wycombe and Birmingham as, it is alleged, they were planning to carry out their own midair explosions was further confirmation, if any were needed, that the al-Qaeda outrages of 11 September 2001 were not isolated acts of extreme aggression against the United States but the prelude to something much greater: the beginning of a new era in which spectacular acts of mass disaster would be used by terrorists to infiltrate and alter human consciousness, the way we think, feel, even dream. The terror of 11 September had, indeed, made a new future possible.

Never again can we watch a plane flying close to a city-centre skyscraper without recalling what happened on that September morning in Manhattan. Nor, on the crush of an early-morning tube train, can we help, in spite of ourselves, from experiencing a frisson of unease whenever we find ourselves pressed up against a young British Asian carrying a bulky rucksack. Such anxiety is irrational and, in the second instance, racist, but it is also increasingly inevitable.

This is because the terrorists are winning. They have succeeded, as DeLillo predicted they would more than 15 years ago, in altering the way we think about the world. Even when their operations are thwarted as they were last week, they achieve a kind of victory in defeat, because we allow our imaginations to colour in the empty spaces of what might have been. We know what might have been, because variations of it have already happened: in Nairobi, in New York, in Bali, in Madrid, in London, in Mumbai. And we know, too, that it will happen again, because we are warned continuously, even as we go about our daily business and try to forget. Deputy police commissioner Paul Stephenson of the Metropolitan Police said that mass murder was last week being planned on an 'unimaginable scale'. But after 11 September 2001, nothing is unimaginable.

As I travelled to work on the tube on Thursday morning, the full details of what was unfolding were still emerging, and yet already you could see the strain on people's faces: the anxiety, the helplessness, the dread of repetition. Here were ordinary commuters whose daydreams were once more being dark-edged by terror.

Anyone disturbed by our present political uncertainty should read Mao II, urgently. The central character is a paranoid and reclusive writer called Bill Gray (DeLillo began the book shortly after his friend Salman Rushdie was forced into hiding). Gray gives no interviews and refuses to be photographed. In retreat, he has become celebrated as much for his invisibility and reluctance to publish as for the books he once wrote. When a famous poet is kidnapped by militants in war-stricken Beirut, Gray is tempted out of seclusion and asked to use his celebrity and influence to help in some way. He agrees to travel to Lebanon to plead at a news conference for the release of the poet but never arrives in the Middle East; on his way from America to London, Gray dies, as if in despair at the futility of his mission.

In truth, there was nothing he could have done to help the poet, because, DeLillo suggests, in an age of mass communications, where the televised image is all-powerful and all-pervasive, writers can no longer 'alter the inner life of a culture. Now bomb-makers and gunmen have taken that territory'.

DeLillo is, I think, broadly correct: no artist, literary or otherwise, can compete with what he calls terrorism's 'raids on consciousness'. Yet what they can do - and this has become the self-imposed challenge of some of our best writers, from Ian McEwan (Saturday) to John Updike (Terrorist) to Martin Amis (The Last Days of Muhammad Atta) - is to show us something of the shape and contours of that new, terrorist-altered inner life.

Writing recently in the New York Review of Books, Joyce Carol Oates suggested that '11 September has become a kind of Holocaust subject, hallowed ground to be approached with awe, trepidation and utmost caution. The reader's natural instinct is to recoil from a purely fictitious treatment of so profound and communal a subject ... the appropriation of a communal trauma for such purposes would seem to be exploitative'.

Yet the duty of any artist of ambition must be to grapple with the defining particulars and issues of his or her time - and there is no more defining issue than 11 September and its long aftermath. If we accept that terrorism has the power to alter consciousness, indeed that, today, this is its very purpose, then surely there is no more pressing challenge than to investigate just how much our consciousness has been altered, and continues to be altered, by the shock of last week and others like it that will inevitably follow as the conflict between disaffected Muslims and the West stretches on and on.

And through investigating just how our consciousness has been altered we can also investigate the terrorist consciousness, as Updike and Amis attempt to do in their new work and DeLillo did long ago. And through this imaginative investigation, indeed imaginative empathy, we may begin to reach a greater understanding of the threat facing us as well as why so many British citizens feel so alienated from the society into which they were born.